Method for reducing shot dispersion

ABSTRACT

A viscoelastic matrix is utilized to hold flechettes or other types of small missiles or shots in a unitary projectile form until the unit emerges from the gun barrel and until it has substantially passed through the blast region area. This reduces scattering of the missiles.

States Patent Thrailkill et al. [451 Apr. 18, 1972 [54 METHOD FOR REDUCING SHOT 3,123,003 3/1964 Lange, Jr. et al. ..102/91 DISPERSION 34,806 3/ 1862 Budd ..102/42 C 12,545 3/1855 Davis ..102/42 C 1 Inventors: Arllgur Thrallklll, Bel Herbert 2,s2o,412 1/1958 Beeuwkes, Jr. et a1. ..102/91 Lewls, Herve de Grace, both of 3,334,588 8/1967 Larsen ..102/42 c [73] Assignee: The United States of America as represented by the Secretary of the Army T b k W l OTZER T E ZEJ ext 00 o o ymer cience; y re .Bi meyer,Jr.; Pub.: [221 Flled- 1969 John Wily & Sons; p. 479- 482.

21 A 1. N 865,838 1 pp 0 Primary Examiner-Robert F. Stahl Attorney-Harry M. Saragovitz, Edward J. Kelly and Herbert [52] U.S.Cl ..102/42 C, l02/D1G.7 [51] Int. Cl ..F42b 7/00 [58] Field of Search 102/42 C, 91, 92.1, DIG. 7 [57] ABSTRACT [56] References Cited A viscoelastic matrix is utilized to hold flechettes or other types of small missiles or shots in a unitary projectile form UNITED S T S P TENTS until the unit emerges from the gun barrel and until it has substantially passed through the blast region area. This reduces 3,059,578 10/1962 Hegge et a] 102/91 Scattering fth missiles. 3,422,761 1/1969 Whnmore ....102/42 C 3,444,813 5/ 1969 Bird ..102/42 C 1 Claims, 4 Drawing Figures PATENTEDYAPR 18 m2 w 1 J owe:

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Mr T M Z METHOD F OR REDUCING SHOT DISPERSION The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

BRIEF SUMMARY The shots or pellets from a shotgun start their scattering as soon as they emerge from the gun barrel. The blast area or region just outside of the muzzle imparts a marked scattering effect. A choke added to the gun barrel helps keep the shots or pellets bunched for a more concentrated effect in a target of a given area. Or a cannister can be used to hold the shots or pellets bunched until the blast region shock tears the cannister apart and releases the shots or pellets.

U. S. Army inventors made progress toward solving the problem by use of a frangible matrix with the missiles (shots or pellets) embedded therein, (see U.S. Pat. No. 3,059,578, E. N. Hegge et al., Oct. 23, 1962). However, in the Hegge patent, it is essential" that initiation of the disintegration occur during the interval of passage through the muzzle blast area, (Col. 5, lines 55-60). Thus, scattering begins and is accentuated by the muzzle blast.

By way of contrast, the present invention prevents disintegration of the frangible multimissile projectile until after it has substantially passed through the blast area or region. The delayed action is obtained by use of a viscoelastic matrix binder having a viscosity index or strength adequate to prevent emergence of the missiles as the multimissile projectile passes through the blast area. The matrix permits the missiles to emerge from the projectile in the tail end or soon after it has passed through the blast area. Beyond the blast area the projectile is no longer subject to the turbulent scattering forces and strong tail winds encountered in the blast area. Therefore, in the present invention, the individual missiles remain more closely bunched and travel farther, delivering more missiles into a target of a given size at a given distance. Of course disintegration of the bulky binder matrix, and release of the captive shots or flechette missiles, permits the individual missiles to go forward at maximum velocity, not impeded by air resistance against the matrix.

The advantages of the present invention are even more significant where the missiles are flechettes, or arrow-like darts. The individual flechettes are not blasted apart into a scattered random array, and they do not tend to turn around and head into the tail wind" caused by the muzzle blast effects. Nevertheless, they are released at the tail end or soon after the projectile passes out from the blast area. The individual flechettes or darts then offer less air resistance, remain headed straight forward, and each travels farther than they would if the packaged projectile, with its large area and consequent high air resistance, had held the flechettes captive for a greater distance.

For some specialized purposes a slightly less viscous binder may be used so that disintegration may begin in the tail end of the blast area. Or, a more viscous binder may be used to delay the action considerably past the blast area.

In the drawing:

FIG. 1 illustrates initiation of disintegration of a previously known multimissile projectile;

FIG. 2 illustrates initiation of disintegration in accordance with the present invention;

FIG. 3 illustrates introduction of the elastic binder to the shell to surround the missiles;

FIG. 4 illustrates flechette missiles in accordance with the present invention.

Prior inventors have taught the use of a matrix binder 1 which holds missiles 2 together to form a projectile 3. The projectile 3 and wad 4 are forced out from gun barrel 5 by highpressure gases which create a blast area or a blast region 6. This blast area or region may extend outwardly only a few inches from a small bore gun and light duty powder. Or, it may extend many feet from a large gun with heavy duty or a heavy charge of powder. This region of violent blast efiects is utilized in the prior patent to Hegge to initiate disintegration of the projectile. However, the individual missiles are thereby thrown outwardly and scattered, thereby resulting in fewer missiles striking a given target. If the individual missiles are flechettes or darts or arrow-like projectiles they go sailing off in all directions, and try to turn around to face the strong tail wind in the blast area, thereby further reducing the concentration of projectiles striking a given target. If the previous matrix were made so strong as to resist the blast area effects there would not be any other forces along the flight path which are strong enough to disintegrate the projectile and release the missiles. Further, if the projectile does not disintegrate soon after passing through the blast area its large size and aerodynamic drag would sharply reduce its velocity and range. Therefore, as to prior art exemplified in the Hegge et al. U.S. Pat. No. 3,059,578, it is essential" that initiation of disintegration occur during the interval of passage through the muzzle blast area.

FIG. 2 illustrates a new approach that minimizes blast area scattering by passing multimissile projectile 7 completely, or substantially, through the blast area 6 before initiation of disintegration. Initiation of disintegration, in this discussion, is taken to be the point at which missiles 2 begin to escape from the viscoelastic binder material 8. The disintegrating forces, such as blast area effects, tail winds, pressure from wad 4, resistance of air, and so on, tear the projectile apart relatively slowly, instead of violently exploding it in the blast area as in the prior art. In other words, the viscoelastic binder is more slowly stripped, by head winds beyond the blast area, and is distorted and torn apart a split second later than in prior art devices without the missile exploding in the blast area.

For some applications the missiles should be released earlier than for other applications. As mentioned above, the blast area may extend a few inches, or several feet, from the gun barrel, depending on powder charge and strength, gun size, and so on. Also, for some applications it may be desirable to initiate disintegration in the tail-end of the blast area while, for other applications, it may be desirable to suppress disintegration for a greater extent until the projectile travels farther toward the target.

Example:

The elastic matrix (viscoelastic binder material) 8 may comprise a plastic monomer or prepolymer such as silicone RTV-ll, a silicone rubber made by General Electric Co. A chemical monomer, Dimethyl Dihydroxy silane, is polymerized, through dehydration, to Dimethyl poly Siloxane. A catalyst (accelerator) such as Dibutyl Tin Dilaurate is used. Approximately 4 drops of catalyst is used per 50 grams of monomer. (Other amounts of catalyst may be used to achieve various degrees of hardness or various lengths of cure time, and so on). FIG. 3 illustrates potting the shots in a typical shell casing. A hollow needle 9 (commonly known as a hypodermic needle) is used to inject the monomer-catalyst mix 8 through the side of the shell casing 10 near the bottom of the shot column. The mix is forced upward, filling the interstices of the shot column. The upper surface 11 of the rising plastic matrix forces the air out from the top of the shell casing. The matrix is allowed to cure, (for example 72 hours for 4 drops of catalyst per 50 grams of monomer). The resultant silicone rubber has a shore hardness of about 10.

, A shot shell, produced as set out above, performed as follows. A target 4 feet by 5 feet was set at a distance of 50 yards from a shotgun muzzle. Each round of ammunition (each projectile) contained 27 pellets or shots, No. 4 Buck shots, in a 12 gauge shell. The dispersion for the various tests was recorded as the smallest circle containing 14 pellets or shots, say 50 percent of the original pellets or shots. (This is a circular probable error type of measurement). Also shown is the total number of pellets striking the 4 foot by 5 foot target.

No. of pallets in 4'X Radius of circle Gun A is the standard Army riot shotgun. Stevens Model 620 having a 20-inch barrel. cylinder bore, and no choke.

Gun B is a commercial shotgun, Winchester Featherweight having a 26-inch barrel and a full compensated choke.

"(Gun B) The MK 5 shell (Special) is the bestexperimental ammunition from a commercial source. It contains a plastic sleeve.

A comparison of lines 1 and 2 in the table shows the effectiveness of the matrix. The Army riot gun with the Remington shell had a dispersion at 50 yards so that less than half the shots (l out of 27) struck the 4 X 5 foot target. With the addition of the matrix and with the same gun/shell combination, 25 to 27 pellets struck the target and of these, 14 were in a circle of radius inches to 12 inches. Line 3 shows that a gun with a longer barrel, a full choke and the best obtainable commercial experimental ammunition did not equal results obtained with the present invention.

From the foregoing, it is seen that the elastic matrix of the present invention, which holds the multimissiles together, at least during transition through the most violent portion of the blast area, achieves very desirable results. It causes a simple shotgun and shell to give performance superior to a precision shotgun and choke combination. Simple (cylinder bore) guns shoot as well, or better than, the more expensive guns. Shorter barrels can be used. Mechanical attachments (subject to wear), such as chokes, are not needed.

With conventional ammunition high muzzle pressure would force the rear wad through the shot column and cause severe scattering just as soon as the shots emerged from the confining walls of the gun barrel. Therefore, low muzzle pressure, with consequent short range, was necessary. The present invention permits very high muzzle pressure and consequently, greatly increased range.

FIG. 4 illustrates the invention wherein the missiles 2' are flechettes or other small sharp edged missiles, pushed by pusher plate 4', with a rigid plate near the missiles. As these small dart-like arrows emerge from the viscoelastic binder 8 they have a very high forward velocity and fly or sail substantially straight forward toward the target. They do not tend to turn around and head into the high velocity blast area tail wind." They are not blasted radially outwardly as in the case of a multimissile projectile exploding in the blast area. The viscoelastic binder 8 is more slowly shed by aerodynamic stripping from head winds. Therefore, a much higher percentage of the flechettes strikes the target.

Tests were made of rounds of ammunition containing three flechettes each. The results were as follows:

The range to target was l6 yards, and the target was 4 feet by 4 feet. The numbers called x and y are horizontal and vertical coordinates, in inches, of the impacts measured from the upper left-hand corner.

Without Potting Matrix y No. of Hits Round l 140 15.9 2

Round 2 31.0 14.0 3

Special Note: All of the flechettes impacted sideways, i.e., flat on the target.

With Potting Matrix y No, of Hits Round 1 20.8 18.9

28.8 2L3 Round 2 21.4 27.0 3

Special Note: All of the flechettes impacted straight, i.e.. nose first on the target.

The reason the matrix method is so effective for flechettes is the following. A flechette, or any fin-stabilized object such as an arrow, behaves exactly like a weathervane; i.e., it wants to line itself up with the direction of the wind. Consider flechettes just as they emerge from the muzzle without the matrix protection or some form of protection which is stripped away by the muzzle blast. At the instant of emergence, and for a short time thereafter, the muule gases are moving faster than the flechette. Therefore, to the flechette it seems to be flying backward; i.e., it senses a wind blowing from its rear. Consequently, it tries to turn around to align itself with this rearward wind. Before it can completely do so, however, it has passed through this muzzle region and into air which it is rushing through. Now it finds itself misaligned to this new wind from the front and turns to line up with this wind. These gyrations are what lead to the poor flight path and large disperstem.

The potting matrix shields the flechettes from the muzzle wind" not releasing the flechettes until they are in the air through which they are supposed to fly.

It will be noted that the flechettes without the matrix impacted sideways, flat on the target, and one missile completely missed the target. With the potting matrix all missiles landed on the target, nose first.

A specific example of an elastic matrix has been set out, including its contents, method of preparation, method of introduction into the projectile of missiles. Also, specific examples of the effects it has on behavior of the small missiles are set out hereinabove. However, many other forms of elastic matrix could be used, such as polyurethane, and so on. Other methods could be used for introducing the material to fill the voids among the missiles. More viscous binder materials could be used to delay initiation of disintegration. Less viscous binder materials could be used to release the missiles earlier after the muzzle blast peak has been passed. Darts, flechettes, or other sharp fragments could be used. For hot desert conditions one elastic binder may be optimum while another binder may be optimum for cold arctic conditions. It is believed that engineering the system for the desired characteristics and optimum results for a given set of conditions is within the skill of experts in this art.

We claim:

1. A multimissile projectile adapted to be fired from a shot gun at high velocity and high muzzle pressure consisting essentially of a plurality of flechettes embedded in a viscoelastic matrix material selected from the group consisting of a silicon rubber and a polyurethane, so that the matrix material substantially fills the interstices between the flechettes; whereby on firing of the projectile, the matrix material having a viscosity index sufficient to prevent the emergence of the flechettes from the matrix material until the projectile has passed through the blast area. 

1. A multimissile projectile adapted to be fired from a shot gun at high velocity and high muzzle pressure consisting essentially of a plurality of flechettes embedded in a viscoelastic matrix material selected from the group consisting of a silicon rubber and a polyurethane, so that the matrix material substantially fills the interstices between the flechettes; whereby on firing of the projectile, the matrix material having a viscosity index sufficient to prevent the emergence of the flechettes from the matrix material until the projectile has passed through the blast area. 